Although osteoporosis is most common among Caucasian postmenopausal women, it is not infrequent among non-Caucasian women, particularly Chinese and Chinese American women. Chinese Americans are a growing population at risk for osteoporosis. The US Census Bureau estimates by 2050, one-tenth of the US population will be of Asian descent, many Chinese American. Osteoporosis is clearly an important public health problem among Chinese Americans. However, most epidemiologic data that relates bone mineral density (BMD) to fracture risk has been acquired among postmenopausal Caucasian women and it is, thus, only for this group that the densitometric definition of osteoporosis and treatment guidelines strictly apply. It s not known how BMD relates to fracture risk in the Chinese population nor what T-score accurately describes the population at risk. In the absence of prospective data, the T-score definition of osteoporosis or postmenopausal Caucasian women has been applied to other racial groups. Moreover, a Caucasian BMD referent database is used to assess fracture risk among Asian women. It is becoming increasingly apparent that racial differences in BMD and fracture risk make application of this definition and the Caucasian database problematic. For example, Chinese women in Asia and the US have a significantly lower rate of hip fracture than Caucasian women, despite the fact that areal BMD is lower among Chinese women. These findings suggest that the relationship between BMD and fracture risk may differ among Caucasian and Chinese women. The overall goal of this proposal is to characterize areal bone density as well as other aspects of bone quality, such as volumetric density, bone size, bone microarchitecture, remodeling, mineralization density, hydroxyapetite crystal size and matrix properties among Chinese American women. Comparing these new data to that of Caucasian women may provide insight into how, despite lower BMD, Chinese women are seemingly protected against hip fracture. This new knowledge may permit fracture risk to be more accurately determined among Chinese American women and may allow for the development of diagnostic and treatment guidelines that are directly relevant to the Chinese American population. This project will, in addition, enable me to acquire both the technical and research methodological skills necessary to develop into an independent investigator in metabolic bone disease.